In a Code Division Multiple Access (CDMA) system and an Orthogonal Frequency Division Multiplexing (OFDM) system, a scheme employing a frequency reuse rate of 1, in which all cells use the same frequency band, is used to increase the capacity of a cellular communication system. When all cells use the same frequency, there is a problem in that inter-cell interference causes the capacity of a cell boundary area to decrease.
FIG. 1 illustrates a cellular communication system.
Two base stations 102 and 112 are located in two cells 100 and 110, respectively, and a plurality of user equipments (UEs) 104, 106, and 108 are distributed in the cells 100 and 110.
In order to solve the problem, the fractional frequency reuse (FFR) technology that allows the UEs 106 and 108 located in a cell boundary area to use a frequency reuse rate of 3, and allows the UE 104 located in the center area of the cell to use a frequency reuse rate of 1, has been proposed.
Attempts have been continuously made, even in a Mobile-WiMAX system, to increase the capacity of a UE located in a cell boundary area by applying the FFR technology.
When the FFR technology is applied, a frequency pattern suitable for each cell is determined by a cell planning tool (or an equivalent) at the time when a base station is built, and the determined pattern is used fixedly (i.e. without a change). However, in an actual environment, distribution of users (i.e. UEs) shows different characteristics depending on cells. That is, while the distribution of UEs in a cell is concentrated on a cell boundary, the distribution of UEs in another cell is concentrated on the center of the cell. Also, such a distribution of UEs may vary as time passes.
In order to efficiently use resources, it is necessary for an FFR frequency pattern to vary depending on the changing UE distribution. However, since the conventional FFR technology uses a fixed frequency pattern, it is impossible to accurately reflect the characteristics of the changing UE distribution. Specifically, a non-uniform UE distribution environment reduces the efficiency of resource usage.
Recently, in a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, an attempt has been made to reflect a dynamic cell characteristic therein by exchanging load information of cells through the use of an X2 interface between base stations. However, since the amount of exchanged information is limited, there is a limitation in efficiently controlling inter-cell interference with the limited information.